Conventional scraper bowl structures typically include a pair of sidewalls, a forwardly extending bowl floor, a rear ejector, and a front apron. In operation, the entire bowl structure, including the sidewalls, is pivoted around the supporting rear wheels from a raised load-carrying position to a lowered loading position. In the loading position, the front edge of the rigid bowl floor scrapes earth into the rear portion of the scraper bowl structure until the desired load is obtained, whereupon the apron is pivotally lowered to close the bowl structure and the entire bowl structure pivotally raised to the load-carrying position. Upon reaching the desired site, the bowl structure is pivotally lowered, the apron raised, and the ejector urged forwardly to displace material from the rear of the bowl structure.
While the aforementioned scraper bowl structure has been widely accepted, it is relatively complex and costly in construction. In addition to requiring movement of the ejector and apron, the entire bowl structure must be pivotally raised and lowered, and this leads to complex supporting systems at the front end thereof. For example, pairs of undesirable draft arms extend around the sidewalls of the bowl structure so that the bowl structure can be pivotally raised and lowered, and expensive hydraulic jacks are required to perform this function.
Another problem with conventional scraper bowl structures is that, in the loading mode, earth enters over the cutting edge of the bowl floor and soon accumulates such that earth is forced upwardly against earth. This frictional retardation requires more loading energy and is time-consuming.
U.S. Pat. No. 2,567,534 to C. Whittier on Sept. 11, 1951, discloses one bowl structure having a rear blade that advantageously loads onto a front apron. However, the rear blade is rigidly secured to the supporting frame so that it is necessary to pivotally raise and lower the bowl supporting frame. This requires an undesirably complex and costly construction.
U.S. Pat. No. 2,858,627 to A. J. Brown et al on Nov. 4, 1958, discloses another bowl structure desirably having only a movable front apron bowl and a movable rear main loading bowl. But, the support therefor must also be raised and lowered, and earth soon accumulates at the front edge of the rear bowl during loading until the entire mass must be forced upwardly and rearwardly in much the same way as a more conventional bowl structure.
Accordingly, what is desired is a scraper bowl structure which does not have to be raised and lowered as a unit, which has a relatively few number of pivotal components, and which can be relatively easily loaded and unloaded for effective economy of operation and the saving of energy.